Extreme slowdown with VM using more than 1 CPU

[waldorfm]

Hello,

I have a virtual machine with the latest update of Oracle Linux 6, UEK 3 kernel and Oracle 12cR1 ASM and DB installed. The VM gets very slow already when there is only moderate work-load. As it turns out, the problem only occurs when there is more than 1 CPU assigned to the VM. I have not been able to find any reasons otherwise related to I/O or CPU usage that explains the extreme slowness.

The VM was previously set up and configured for VMware Fusion 6, where it was running great in the same configuration with 8 GB of RAM and 4 CPU's assigned. I previously ran into issues creating this VM under VirtualBox 4.3.16 under Mac OS X, also when multiple CPU's were assigned, but it was a different system and different problem: https://www.virtualbox.org/ticket/13476

Since I like VirtualBox, I set up another 8-core Mac Pro and thought I give VirtualBox 5.0.10 under Windows 7 x64 a try, running as the host system native on the machine. I exported the VM using OVF under WMware Fusion under OS X 10.9.5 and imported it into VirtualBox 5.0.10 under Windows 7. I had to fix a problem with the configuration of the Ethernet adapter and assigned all the 16 virtual drives (ASM) to a virtual SATA controller. I also converted the vmdk disk images to vdi using VBoxManage. When I boot the system with 1 CPU assigned, it works OK, but with 4 CPU's assigned it becomes unresponsive. VMSTAT and IOSTAT does not show anything unusual. The system becomes so slow that a "ps" or "top" takes minutes to complete.

VirtualBox is installed on a Mac Pro 8-core (2007) with 2 Intel Xeon X5365 3 Ghz quad core processors. The system is using an ARECA ARC-1212 storage controller with 3 WD RE4 2 TB disks, RAID-5. The machine has 16 GB of RAM and a Nvidia GTX 680 video adapter, running Windows 7 SP1 x64. There is no other virtualization product installed or anything else running and the system is otherwise performing well with any of the latest state of the art computer games with ultra quality settings.

The result with VirtualBox is disappointing. Is this a know issue with multiple VM CPU's? I seems that this has been a long standing issue. Is there any way to solve or troubleshoot the problem other than switching to VMware again?

Thanks!

[frank]

It depends always how many CPUs you assign to a VM and how many host CPU cores your host has. VirtualBox has still deficits with multi-CPU guests but 2 or 4 VCPUs usually work well (never use 4 VCPUs on a system with 2 host cores and 2 HT per core!).